Phase evolution characteristics of FeCoCrAlCuVxNi high entropy alloy coatings by laser high-entropy alloying

Abstract

Fe, Co, Cr, Al, Cu and V powders with close-to-equiatomic ratios were mixed and laser surface alloyed onto Ni201 substrates aiming at producing FeCoCrAlCuVxNi (x=0, 0.2, 0.5, 0.8, 1) coatings. With optimized processing parameters, the laser high-entropy alloying (LHEA) coatings with good metallurgical bonding to the substrate were achieved. X-ray diffractometry confirmed that the crystal structures of FeCoCrAlCuVxNi LHEA coatings evolved from single phase fcc for 0≤x≤0.2 to duplex of fcc and bcc for 0.5≤x≤1. The phase formation of the FeCoCrAlCuVxNi LHEA coatings was analyzed based on rules of high entropy alloy coatings. It was found that the formation of single phase solid solution structure was governed by the competition outcome of mixing entropy (ΔS), mixing enthalpy (ΔH), atom-size difference (ΔR), valence electron concentration (VEC) and electro-negativity difference (ΔX), instead of the VEC values as suggested previously.